I recently saw someone trying something like this on a local free-ad website.

Seller had an older HK receiver listed for a reasonable price. Not blowout, but probably fair. I called, got a machine and left a message.

Later in the day I checked the ad, and the price had increased by $10. Of course, had the seller bothered to call me (never happened, of course) I would have responded that I was not interested in bidding. I should have flagged it, but didn't even think of it.